In recent years, a three-dimensional survey of a three-dimensional object is frequently conducted, and demand for images with three-dimensional data of a three-dimensional object has increased. Therefore, at a survey site, by using a laser scanner, a pulsed laser is scanned on a predetermined measurement area and distance measuring is performed for three-dimensional position data of an irradiation point of the pulsed laser to acquire point group data of the measurement area (for example, refer to Patent Literature 1).